Marine growth on water resident objects such as piers, waterways, oil rigs, water-going vessels, is a significant problem. In water-going vessels, for example, such as ships and boats, marine growth, such as algae, invertebrates (mussels, crustaceans) can cause significant cost, for operators of commercial shipping in particular. Marine growth can result in greater wear and tear, significant increase in fuel consumption if not treated (10%-15%) and substantial maintenance costs.
Attempts have been made to address the marine growth problem by using anti-fouling paints on surfaces, such as ships hulls, likely to be affected. Many anti-fouling paints, however, have been found to be damaging to the environment and many countries have banned or are considering implementing bans on the use of such anti-fouling paints and even on entry of ships bearing anti-fouling paints into the country's waterways. Further, anti-fouling paints can be expensive to purchase and apply and require re-application periodically.
Mechanical scrubbing techniques utilising brush cleaning machines or the like have been used to remove marine growth. Again, however, authorities often ban the use of such equipment due to the environmental effects of infestation of imported marine life in areas where the mechanical cleaning occurs. Further, where a surface has been treated with an expensive surface treatment such as an anti-fouling paint, intensive scrubbing techniques can result in damage to or removal of the surface treatment which can in turn be costly as well as potentially accentuating the environmental damage caused by the scrubbing.
It has been proposed to utilise heat treatment to treat some biological infestations of waterways and equipment used in waterways. U.S. Pat. No. 5,389,266 (Clum et al) discloses an arrangement for treating zebra mussel infestation on the bottom surface of a waterway. A heat exchanger is mounted within a chamber which confines water to an area of the bottom surface of the waterway. The heat exchanger heats the water to kill the zebra mussel infestation. The chamber is then removed from the bottom surface and the process may be repeated at another portion of the bottom surface. This treatment requires the provision of a heat exchanger within the confining chamber.
U.S. Pat. No. 5,389,266 also proposes treating the hulls of water-going vessels, such as ships, by enclosing a hull in its entirety within a chamber and heating the water within the enclosed chamber either by utilising a heat exchanger positioned in the chamber or by passing water from the chamber to an external heat exchanger, heating it and passing it back into the chamber. This method of treating ships hulls would be expensive and impractical for all types of, vessels, particularly large ships. Further, the amount of energy that will be required to heat all the water in a chamber surrounding a large hull may be prohibitive.
Soviet patent publication no. SU 119-924A discloses a method of treating algae on a hull by, firstly, shrouding at least part of the hull in an insulating jacket and then heating the hull from a heat exchanger fitted to the inside of the hull. The heat from the hull is transferred through to the algal growth. Once the algae has been killed, the insulating jacket may be removed.
This arrangement requires the positioning of an insulating jacket about a hull, which may be difficult (particularly for large vessels). It also further supposes that there is access to the inside of the hull to heat the inside of the hull so that the heat is transferred to the outside of the hull. It may be difficult in many vessels to obtain access to enough of the inside of the hull to allow effective treatment of the algae.